Since their discovery, carbon nanotubes have been object of several studies and researches, which revealed their specific physical, chemical, electrical and optical properties. Scientific and commercial interests are closely related to said carbon materials due to their properties.
Single wall carbon nanotubes (SWCNT) can be produced by a variety of methods, such as arc discharge, laser ablation, thermal carbon vapour deposition (CVD), plasma CVD, deposition of CNx films by electrolysis of organic liquids and a reaction with a catalyst carbon paper.
The arc discharge and laser ablation are methods in which a precursor material is constituted by a solid carbon-based material (a graphite rod), wherein it is sublimed at high temperatures (>3600K). The thermal CVD and plasma CVD are methods in which a precursor material is a gas phase (hydrocarbon). Document US 2006/7125525 (Schiavon) describes an apparatus and a method based in an environment wherein a graphite element is sublimed in plasma, under an inert gas that is carried through a high electromagnetic field.
Another thermal CVD method is disclosed in document US 2007/0003471 (Kawabata), wherein the growth of carbon nanotubes on a substrate occurs without increasing residual carbon impurities. This method is also described in document US 2006/0111334 (Klaus), but the nanotubes are formed on a substrate by using a catalytic CVD method.
Yan, X. et al. (Yan, X. et al. “Preparation and characterization of electrochemically deposited carbon nitride films on silicon substrate” J. Phys. D: Appl. Phys., 37(2004), p. 1-7) describes an electrochemical deposition of films in organic liquids, using a large area deposition, a low temperature (about 60° C.), a DC power supply voltage of 800V and a duration of 10 h. A catalyst carbon paper is used in document US 2003/0111334 (Dodelet), wherein nanoparticles are randomly deposited on a carbon substrate and heated.
The methods mentioned above produce a large amount of carbon amorphous and nanotubes, in an uncontrolled and disordered manner. Document US 2007/0140947 (Schneider) describes a method for continuously manufacturing organized carbon nanotubes. However, the method requires a porous substrate (non carbon elements, e.g. Si, N and P) and catalytic particles.
The application of these methods for manufacturing carbon nanotubes requires complex equipments, rigorous experimental conditions, including high vacuum environments and high temperatures. So that these materials produced with Therefore, the carbon materials obtained by these methods present a high cost and a low yield (very small amounts are produced), thus representing an obstacle to their utilization in industrial scale and scientific researches.